Velocity modulated tube with removable resonator



c. v. LITTON 2,293;152 VELOCITY MODULATED TUBE WITH REMOVABLE RESONATOR Aug. 18, 1942.

15, 1940 2 Sheets-Sheet 1 Filed Oct.

FIG-2.

FIGB.

INVENTOR.

ATTORAE'Y VELOCITY MODULATED TUBE WITH REMOVABLE RESONATOR Filed Oct. 15,1940 2 sheets-sheet 2 FIGA, I

' a a J @J INVENTOR.

CHARLES K L/ 7' 7' 0 Patented Aug. 18, 1942 VELOCITY MODULATED TUBE WITH REMOVABLE RESONATOR Charles V. Litton, Redwood City, Calif., assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application October 15, 1940, Serial No. 361,203 2 Claims. (Cl. 250'-27.5)

This inventionrelates to velocity modulated tubes and more particularly to velocity modulated tubes having readily removable closed cavity resonant circuits;

Vacuum tubes have been proposed using the variation in velocity of electrons in an electron beam to produce or amplify high frequency energy. In such tubes it has been proposed to use closed resonant chambers to effect the control of the electron velocity and to extract energy from the beam. These tubes, however, have'a number of disadvantages. The space within the closed chamber is generally part of the tube envelope requiring a large volume to be evacuated. Further, if any fault develops in either'resonant chamber the entire tube becomes faulty.

Moreover, the tuning of the circuits and the waverange of operation of the tubeca'n only be adjusted over a small range limited by the size of the closed resonant circuits and the limited adjustment possible in these circuits.

It is an object of my invention to eliminate some or all of the difliculties outlinedabove.

It is a more specific object of my invention to provide a velocity modulated tube with removable closed resonant circuits, which can be readily replaced and need not be evacuated.

. It is a further object of my invention'to provide a velocity modulated vacuum tube in which the tuning range may be altered by replacing closed circuits tuned to a given frequency by other circuits tuned to a different frequency Without destroying the vacuum within the tube.

It is a still further object of my invention to provide a tuning means for velocity modulated tubes by which the dimensions of external resonant chambers are adjusted to determine a desired resonant frequency.

A better understanding of my invention, as well as the objects and features thereof, may be had from the particular description of certain embodiments thereof made in connection with the accompanying drawings, in which Fig. 1 illustrates an embodiment of my invention;

Fig. 2 illustrates a modified form of my invention, and

Figs. 3 and 4 illustrate embodiments of my invention incorporating adjustable features.

In Fig. 1 is disclosed a form of velocity modulated electron beam tube. This tube includes an electron emitting cathode l which serves an electron gun for producing an electron beam. The electrons emitted from cathode Ill may be accelerated by potentials applied to succeeding porthe tube.

chamber 26. cillator, energy may be fed back over lines 36 tions of the tube. Cathode II] is contained Within an evacuated envelope comprising conductive tubular portions ll, [2, l3, sealed together at M, I5 to provide a continuous tubular arrangement and sealed at one-end by a glass press It and at the other end by a glass seal ll. In the end of tubular elements II and I2 adjacent one another are provided two discs 2|, 22, in which openings are provided which serve to modify the velocity of the electron beam. In the opposite end of tube l2 and the adjacent end of tube l3 are provided two similar discs 23, 24 provided with similar control openings. If desired, these openings may be provided with a grid structure thereacross in order to distribute the potential more evenly across the openings. overlying the tubular portion and in electrical contact with tubular elements and I2, is a first resonant chamber 25. This resonant chamber is tuned to the desired operating frequency and serves to modify the velocity of electrons in the beam at the operating frequency as they pass between openings 2| and 22.

The electrons of the beam after passing grid 22 traverse tube 12 a distance sufficient to insure a bunching of the electrons. As the electron beam passes between the openings in discs 23, 24, energy is extracted from these loops by means of a second resonant chamber removably supported on the evacuated envelope and in electrical contact with tubular elements l2, [3. This second resonant chamber 26 is tuned to the operating frequency and serves to reduce the velocity of electrons in the stream, and extract energy therefrom at the frequency determined by chamber 25 and the grouping of the electrons Within A target electrode 21 is provided for removing the electrons after passing discs 23 and 24 from the tube.

A concentric transmission line having a coupling loop 31, is provided for introducing energy at the operating frequency into chamber 25,

and a similar concentric line 36 and loop 38 is provided for extracting energy from resonant If the tube is to be used as an osand 35. However, if the tube is to be used for amplification the input energy may be applied .at 35 and the extracted energy obtained at lin Since resonant chambers 25 and 26 are removably supported on the evacuated portion of the tube, it is clear that only a small volume need be evacuated. Furthermore, if it is desired to alter the frequency of operation of the system it is merely necessary to provide in place of chambers 25 and 26, other chambers tuned to a different operating frequency. The resonant chambers 25, 26 are made with the inner tubular portion thereof resilient so that they will bear against the tubular portions of the evacuated envelope to make good electrical contact. Good operating characteristics may be achieved with a resonant ratio of 2: 1, since the actual drift distance length is not critical. Furthermore, the variation in speed of the electron beam may be adjusted to in part compensate for the change in drift distance by adjusting accelerating potentials applied to the resonant chambers or to any accelerating electrode within the tube. When the tube is to be utilized at different operating frequenciesas an oscillation generator, it is only necessary to properly adjust the phase of feedback energy in order to accommodate it to the different wave lengths thereof. Phase adjustment may be readily accomplished external of the circuit by means of a telescopic concentric line arrangement. Furthermore, since the resonators need not be evacuated, it is unnecessary to seal the concentric line members.

Fig. 2 illustrates another embodiment of my invention similar to that shown in Fig. 1. However, in this arrangement the evacuated envelope is made substantially wholly of glass as indicated at 40, the only metal portion of the envelope being shown as target electrode l1 sealed to the glass envelope. Within the glass envelope are provided tubular elements HA, IZA, [3A, corresponding to H, l2 and I3 of the structure of Fig. 1. These elements carry discs forthe accelerating and extracting electrodes 2!, 22, 23 and 24, respectively, which also correspond to the similar elements of Fig. 1. Two removable resonant circuits 25, 23 with concentric lines 35, 36 are adjusted on the tube external the glass envelope into a position to provide faster coupling between these chambers and elements A, I2A and [3A to provide the desired A. C.

voltages for the grid openings in discs 2|, 22, 23 M and 24. Chambers 25 and 26 are preferably provided with slotted wall arrangements as indicated at 29 in chamber 26, so that the inner portions thereof will be spring pressed to hold firmly against the glass envelope 40. If it is desired to alter the frequency by substituting resonant cavities having a different tuning, chambers 25and 26 may be removed and others resonant at different frequencies substituted in their stead. If it becomes necessary under these circumstances to alter the electron stream velocity, control of the stream may be effected by means of potential changes on accelerating electrode 4|.

It will be clearly understood that a tube of this type may be readily used as an amplifier or an oscillator in the same manner described specifically in connection with Fig. 1.

It may be desirable to provide a tuning system so that the tuning of the operating potential of the tube may be varied over a wide tuning range without exchanging one resonant cavity for a different one. In Fig. 3 is illustrated a tube provided with removable reasonant chambers which may be adjusted to alter the tuning of the tube with respect to the operating frequency.

In this arrangement the tube envelope may comprise the tubular elements I I, l2, l3, sealed together as in Fig. 1, and provided with grid supporting discs 2|, 22, 23 and 24. Resonant 20 of the circuit.

40 threads on tubular element 45.

63 is rotated element 25B is advanced or withdrawn from a telescopic engagement with part chambers 25, 26, each consist of two parts 25A, 25B, 26A, 263, which are telescopically arranged together so that the operating frequency of the system may be readily adjusted. As previously 5 stated this adjustment should not be greater than in Fig. 1. It should be distinctly understood that this adjustable tuning chamber arrangement may be readily applied to tubes of the type shown in Fig. 1 or Fig. 2. In view of the fact that the chambers 25, 26 do not need to be exhausted the slide connection for altering the tuning thereof is readily accomplished.

In Fig, 4 is shown a tube somewhat similar to Fig. 3 but showing more completely details for mounting the tube and adjusting the tuning In this figure the elements corresponding to elements of Fig. 3 are designated by similar reference characters. On each of'portions B and 26B are provided additional tubular extensions 45, 45, provided with external 25 threading. Likewise, two threaded discs 41, 48

are rigidly fastened to tube l2 and portions 25A and 26A, respectively, are held in place on these discs by threaded connections. These chamber portions 25A, 26A are locked in place on the 30 nuts by means of the focusing coils shown at 5 Rigidly fixed to supporting structure 6|] are ball races 6!, 62. A tuning disc 63 is mounted to rotate with the inner portion of the ball race 6|. Disc 63 is provided with a sleeve 64 which is internally threaded to engage with the external Thus, as disc 25A, to adjust the tuning. Similarly, a threaded control element 61 is associated with the tubu- 45, lar portion 46 for advancing or withdrawing elements 2613 from 26A to accomplish the adjustment of tuning.

While I have described my invention in connection with particular embodiments thereof, it 50 is clear that these are made merely by way of illustration. Many other forms of the tube g structure, as well as other adjusting means for adjusting the tuning will readily present themselves to those skilled in the art. What I consider my invention and desire to protect in my envelope containing means for producing a beam of electrons of a given average velocity, velocity modulating electrodes .in the path of said beam for modifying the velocity of electrons in said beam, drift means for allowing electrons in said beam to become grouped after modification of their velocity, and extracting electrodes for extracting energy from said grouped electrons, a first substantially closed resonant chamber removably mounted externally of said envelope coupled to said velocity modulating electrodes, a

second substantially closed resonant chamber removably mounted externally of said envelope coupled to said energy extracting electrodes, each of said chambers comprising two telescopic sections adjustable for tuning said chambers, and

movably mounted externally of said envelope coupled to said velocity modulating electrodes, and a second substantially closed resonant chamber removably mounted externally of said envelope coupled to said energy extracting electrodes, one of said chambers comprising two telescopic sections, a screw-threaded sleeve carrying one of said sections, and a rotatable disc cooperating with the screw threads axially to displace said 10 sleeve for tuning the chamber.

CHARLES V. LITTON. 

